Transmission



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TRANSMISSION Filed Oct. 21, 1944 2 Sheets-Sheet 2 Patented Apr. 27, 1948 TRANSMISSION y Howard C. Wiemer, Muncie, Ind., assignor to Borg-Warner Corporation, Chicago, Ill., a corporation o! Illinois Application October 21, 1944, Serial No. 559,804

13 Claims.

My invention relates toitransmissions and more particularly to coupling mechanisms in transmission.

In a copending application of Palmer Orr and Carl J. Conkle, Serial No. 488,185, led May 24,

1943, now Patent #2,414,388, January 14, 1947, there is described a two speed transmission having a self-shifting coupling for conditioning the transmission to drive in either one speed ratio or in the other. The self-shifting coupling comprises an element shiftable under the influence cf torque applied to the element .into either of two positions which correspond to the two speed ratios and a locking mechanism for holding the shiftable element in either of its positions. 'I'he locking mechanism includes a ball adapted to fit Vin appropriate grooves in the shiftable element and a ring having a cam for holding the ball in the grooves. This locking mechanism has been found successful where the power transmitted through the transmission is small and where there is a steady application of load and driving torque; however, where there is shock loading and torsional vibration applied to the trans mission as is commonly the case in aircraft installations, it has been found that this ball locking mechanism functions satisfactorily for only relatively short periods oftime, due to the fact that only the curved surfaces of the ball are etlectivefor stopping movement of the shiftable member. x

It is an object of my invention to provide an improved coupling construction which is satisfactory for transmission installations which are shock loaded and have torsional vibrations applied thereto, as, for example, transmissions for aircraft. I

More particularly it is an object of my invention to provide improved locking mechanism of this type in which flat surfaces, as contrasted with curved surfaces, are used as abutments for locking a shiftable element in place.

Stillv more particularly it is an object of my invention to provide an oscillatable blocker having flat surfaces which cooperate with iiat surfaces on a shiftable element to lock the element from movement when so desired.

The i-nvention consists of the novel construetions, arrangements, and devices to be hereinafter described and claimed for carrying out the above stated objects and such other objects as will appear from the following description of a certain preferred embodiment illustrated in the accompanying drawings, wherein:

Fig, 1 is a longitudinal sectional view of a trans- 2 mission embodying the principles of the invention and taken along line I-I of Fig. 2;

Fig. 2 is a sectionai view taken on line 2-2 of Fig. l;

Fig. 3 is a sectional view taken on line 3-3 of Fig. 1;

Fig. 4 is a developed sectional view taken on line t-t of Fig. l.: andl Fig. 5 is a sectional view taken on line 5-5 of Fig. 1.

Like characters of reference designate like parts in the several views.

My invention is described particularly with reference to a transmission for airplanes which is shown in the accompanying drawings. 'Ihe illustrated transmission comprises a drive shaft ill which may be connected directly to the engine or other source of power (not shown), a driven -shaft II adapted to be connected to a propeller (not shown), a double reduction lplanetary gear set I2 adapted to provide a reduced drive between drive shaft IB and driven shaft II and a coupling device I3 for effecting the changes in ratio through gear set I2. The entire mechanism is enclosed in a housing I4 which may be mounted between the propeller and engine.

The gearing comprises a drive plate I5 segear I6. The ring gear I6 meshes with and drives one or more planet pinion gears Il which are the smaller of pairs of gears formed integrally as a spool and mounted to rotate about pinion shafts i3. A carrier I9 supports pinion shafts I8 and is mounted on and drives splines 20 in driven shaft l l. The planet pinions Il mesh with a sun gear 2l drivingly associated with a sleeve 22 at an end of the latter. The sleeve 22' is rotatably mounted on the drl'ven" shaft II and is formed with teeth 23 at itsopposite end as shown so that the sleeve may function as a reaction member, as will be described.

The larger of the pairs of pinion gears is shown at 24, and the larger pinion gears mesh with a sun gear 25. 'I'he sun gear 25 is rotatably supported on the sleeve 22 and is formed with teeth 26 as shown, so that the sun gear also may function as areaction member as will be described.

The coupling I3 comprises a stationary member 2l which is made up of two portions 28 and 29. A coupling element 30 which comprises two` portions 3I and 32 and which is helically splined to the stationary member 21 is disposed between the member 21 and the reaction members 22 and 25 of the gear set I2. The portions 3| and 32 of the coupling element are provided with teeth 33 and .cured to the drive shaft Ill and driving a ring 34 respectively, and the coupling element 33 is shiftable so that the teeth 33 may mesh with the teeth 26 of the reaction member 28 and the teeth 34 may mesh with the teeth 23 of the reaction member 22. The coupling element 30 when meshing with the teeth 28 functions to hold the reaction member 23 stationary, and the gear set i2 is of such construction that a high speed drive, which is, however, of less thanone to one ratio, is provided from the shaft I Il to the shaft I I. The coupling element 30 when engaging with the teeth 23 functions to hold the reaction member 22 stationary, and the gear set I2 under this condition provides a low speed ratio from the drive shaft I to the driven shaft I. The portions 28 and 29 of the stationary member 21 may be fixed with respect to the housing I4 lby any suitable means, as by means of bolts 35. The portion 28 is provided with helical 'splines 33 and the portion 29 is provided with helical splines 31 (see Fig.' 4). As will be noted from the drawings, the splines 38 and 31 extend in the same direction and in eilect form continuations of each other, so that the portions 28 and 29 function as a single member.

The coupling element portions 3| and 32 are provided with helical splines 38 and 39 respec- 4 41 swiveled and connected to the blocker and extending outwardly thereof through a. suitable slot 48 provided in the stationary portion 28. The stud 41 is connected with Aa rock arm 49 by means of a shift rod 53. The rod 63 at one end has a pivotal connection 5| with the rock arm 43, and the rod 50 at its other end has' a universal connection 52 with the stud 41. The connection 82 may be of any suitable type, such as one utilizing a round bar 53 rotatably disposed in a suitable cavity within the stud and through which the rod 50 extends and is slidably disposed. A

f spring 34 is disposed about the rod 50 and functively, and as will be noted. these splines vextend in the same direction and interengage with the splines 33 and 31 of the portions 28 and 29. 'I'he coupling element portions 3| and 32 are movable toward each other, and a spring 40 is disposed between them for yieldingly maintaining the portions apart. A plurality of retainer yokes 4| are disposed about the outer periphery of the coupling portions 3i and 32 in appropriate slots provided in the portions, and these yokes function to limit the movement of the portions away from each other. The yokes 4| are preferably fixed with respect to one of the portions 3| as by means of pins 42. The coupling element 3U moves longitudinally of the transmission, as will be hereinafter described, with the splines 33 and 39 moving between the splines 33 and 31, and an abutment ring 43 is provided at one end of the stationary member 21 and an abutment ring. 44 is provided at the other end of the member 21 for limiting movement of the coupling element in both directions.

Referring to Fig. 5, it will be observed that the teeth 26 have beveled ends 26a; the teeth 23 have l plete neutral condition, all as will be hereinafter fully described.

A blocker 45 is provided for blocking 'movement of the coupling element portions 3| and 32.

The blocker is in the form of an annular ringV disposed in a suitable groove within the stationary member 21` and between its portions 28.

tions to yieldingly maintain the rod at an outer limit of its movement with respect to the universal connection 52. The movement of the rock arm 43 is limited by means of a pin 55 ilxed within the housing I4 and extending into a suitable slot 38 of the rock arm. The rock arm 49 is connected by means of a shaft 51 with a shift lever 58 on the outside of the housing I4 which is utilized forconditioning the transmission for either its high or its low ratio, as will be described.

The operation of the transmission including its coupling I3 is as follows: The drive shaft I0 is driven fby the attached motor (not shown) In a clockwise direction as viewed from the motor end of the transmission or as seen in Fig. 3 and as is designated by the arrows A in Figs. l and 3. With the condition of the coupling I3 as shown, in which the teeth 33 of the coupling element 30 are in engagement with the teeth 26 of the reaction member 25 of the gearing, the high speed power train is completed through the transmission. The reaction on the coupling element 30 through the teeth 26 and 33 when the motor is driving is in a counterclockwise direction as viewed from the motor end of the unit, that is, in the direction indicated by the Iarrows Bin the drawings. Such a reaction on the coupling element 30 and particularly on its portion 3| tends to move the element 33 toward the front end of the transmission or toward the left as seen in Fig. l with the splines 38 of the portion 3l sliding between the splines 33 of the stationary member 2l. Such movement of the coupling element 30, is, however, prevented by the blocker 45, when the blocker is in its high speed position in which it is shown in the drawings. In this position of the blocker, its splines 46 are in the way of the splines 38 so that the portion 3| cannot move forwardly of the transmission. When the throttle of the driving motor is closed, the reaction on the coupling element 30 is in the opposite direction, that is, in a clockwise direction indicated by the arrows A,

and the coupling element portion 3| tends to move rearwardly of the transmission. This movement is, however, prevented by the ring 43. When the blocker 43 is in its illustrated position, the teeth 26 and 33 thus remain engaged regardless of whether the motor is driving'or a coast condition exists, and the transmision is locked in high speed ratio.

When it is desired to shift the transmission into its low speed ratio, the shift lever 58 is actuf ated to move rock arm 43 into its low speed position as is indicated in Fig. 2. Such movement of the rock arm 49 compresses the spring 54, and the link 50 travels through its universal connection 52 with the stud 41. The blocker 45 and its stud remain in their positions in which they are shown, since the reaction with the motor driving remains the same on the coupling element portion 3|, and the splines 38 of the por- Y The blocker splines 46 thus move against the splines 38 of the coupling element portion 32. which are in the annular groove provided in the stationary'member 2'I for the blocker, and unblock the splines 38 of the coupling element'portion 3|. Thereafter, on `an openingv of the throttle which increases the torque applied to the shaft I8, the reaction on the portion 3| in the counter-clockwise direction indicated by the arrows B causes the portion 3| -to move forwardly of the transmission, with the splines 38 passing between the splines 36 of the stationary member 21. The teeth 33 thus move out of mesh with the teeth 26 to thereby break the high speed power train through the transmission.

While the high speed power train is completed through the transmission land until the speed of the shaft I8 has been raised suihciently after the breakage of the high speed power train by disengagement of the teeth 33 and 26, the reaction member 22 and its teeth 23 rotate in the clockwise direction as indicated by the arrows A in the drawings. When the teeth 33 move out of mesh with the teeth'26, the teeth 34 move into contact with the teeth 23; however, due to the beveled tooth sides 23a and 34a. of the teeth 23 and 34, the teeth 38 ratchet over and do not interengage with the teeth 23. In this condition of the coupling i3, the spring t8 isvfiexed, and neither the low nor the high speed power train is completed through the transmission. When the speed of the drive shaft is increased 'suiilciently so that the shafts i8 and ii are rotating in substantially the low speed ratio with respect to each other, the reaction member 22 and its teeth 23 cease to rotate in the clockwise direction indicated by the arrows A and begin to rotate in the opposite direction indicated by the arrows B. On such reversal of direction of rotation, the teeth 3d cease ratcheting over the teeth 23 and slide into interengagement with the latter teeth. The low speed power train isthus completed through the transmission. When there is a drive in low speed ratio through the transmission, the reaction on the coupling element portion 32 is in the counter-clockwise .direction indicated bythe arrows B, and the splines 33 of the portion move through the splines 3l of the stationary member 2l to the limits of their movement forwardly of the transmission against the abutment plate 84.

With the transmission being in low speed ratio, when the splines 38 move tothe forward limits of their movement against the abutment plate 44, the blocker ,45 moves clockwise slightly as indicated by the arrows A until the blocker splines 46 contact the splines 38 of the coupling element portion 3| which now are in the annular blocker groove in the stationary member 21, and the blocker blocks movement of the splines 38 and of the portion 32 rearwardly of the'transmission. The blocker 45 thus locks the transmission in low speed ratio.

When it is desired to shift from low speed ratio to high speed ratio, the shift lever 58 is moved accordingly to bring the rock arm 49 into its posi- 3| which extend into the annular groove provided for the blocker. The splines 39 of the coupling element portion 32 are thus unblocked, and immediately upon a. closure of the throttle for the engine to decrease the torque impressed on the drive shaft |8, the coupling element portion 32 moves to the rear of the transmission with its splines 38 sliding between the splines 31, due to the reaction on the reaction member 22 changing to the clockwise direction indicated by arrows A, to dlsengage the teeth 34 with the teeth 23. The low speed ratio power train through the transmission is thus broken.

While the low speed ratio is completed through the transmission and until the drive shaft |8 has decreased in speed to bring the ratio of the shafts |8 and to the high` speed ratio as determined by the gear set 2, the reaction member 25 and its teeth 26 are rotating in the counterclockwise direction as indicated by the arrows B. The chamfered ends of the teeth 33a and 26a are effective when this condition exists to maintain the teeth 33 and 26 disengaged and to limit the rearwardmovement of the coupling element portion 3|; however, when the speed of the shaft i8 decreases suiliciently so that the high speed ratio exists between the shaft VIll and ii, the reaction member 25 and its teeth 26 stop and begin to rotate in the opposite direction, that is, in the clockwise direction indicated by the arrows A. On such rotation, the teeth 33 move into interengagement with the teeth 26 to complete the high speed ratio through the transmission. With the throttle remaining closed, the reaction on the portion 3| remains in the clockwise direction so that thesplines 38 are effective to move the coupling element portion 3| to engage with the abutment ring 83. When the splines 38 and the coupling element portion 3i thus move to their rearward limit of movement, lthe blocker element t5 underI the action of the spring 5t oscillates slightly in the counter-clockwise direction indicated by arrows B so that its splines it move against the splines 38 and the blocker is in its original position in which it is shown in Fig. 4 to thereafter block movement of the coupling element portion 3| forwardly of the transmission. The throttle may thereafter be opened for driving the shaft through the gearing i2 from the shaft i8. The thrust is then again on the splines 46, and a driving connection in high speed ratio is complete through the transmission.

The teeth 26, 33, 38, and 23 are beveled, as shown particularly in Fig. 5, to facilitate the shifting of the coupling mechanism and to assure that the transmission can never be in a complete neutral condition. The arrangement of the yokes di, the coupling element portions 3| and 32 and the teeth 23 and 26 is such that either one or both of the sets of teeth 33 and 34 at all times contact with either one or both of the sets of teeth 23 and 26. When the coupling element 38 is in the exact center of its Yshifting movement, the beveled ends 33aand 34a are both in contact with the beveledends 23a and 26a of the teeth 23 and 26, and the spring 48 maintains the teeth in ratcheting engagement. When the shafts |8 and are rotating at a ratio in between the high and low speed ratios provided by the gearing i2, both sets of teeth 33 and 34 will ratchet on the sets of teeth 23 and 2B. The speed of the shaft ii, however, cannot exceed its speed that would be provided by the high speed ratio of the gearing without a reversal in the direction of rotation oi the reaction member 2B and engagement of the teeth 33 and 26, and the speed of the shaft li cannot decrease below the speed that would be provided by the gearing I2 in low speed ratio without a reversal in the direction of rotation of the reaction member 22 and engagement of the teeth 34 and 23. It will thus be apparent that, with this arrangement, the propeller and its shaft il is never at any time free of the shaft i and an engine connected therewith.

The blocker 45 advantageously presents the flat sides of its splines 48 to the'spllnes 38 and 39 of the coupling element portions 3| and 32 for preventing movement of the portions 3| and 32 caused by the spiral splines 38 and 31 of the stal 'tionary member 2l. This blocker construction is such as to take a high thrust thereon which permits high torque to be transmitted through the transmission.. and it furthermore continues to function effectively for long periods of time with shock loading and torsional vibrations impressed on the drive and driven shafts, as would commonly be the case in aircraft installations.

I Wish it to be understood that my invention is not to be limited to the specific constructions and arrangements shown and described, except only insofar as the claims may be so limited, and

` it will be apparent to those skilled in the art that changes may be made without departing from the principles of the invention.

I claim:

l. In power transmission mechanism, the combination of two relatively rotatable members and means for coupling said members together, said means comprising a coupling element effective between. said members and adapted to be shifted in response to changes in relative direction of torque'betweenthe members, and an oscillatable blocker having blocking portions effective in one position to prevent uncoupling movement of the coupling element and in another position of the blocker to allow uncoupling movement of the coupling element.

2. In power transmission mechanism, the coml bination of two relatively rotatable members and means for coupling said members together, said means comprising a coupling element between said members, teeth on said element and on one of said members for coupling the element and member together, said element being coupled to the other member so that it is shifted in response to changes in relative direction of torque between said members and transmitted vthrough said teeth, and an oscillatable blocker having said members, teeth on said element and on one of said members to couple the element and member together, said element being spirally splined to the other of said members and being thereby adapted to be shifted in response to changes in relative direction of torque between said members and impressed on said element through said teeth. and an oscillatable blocker having blocking portions effective in one position of the blocker to prevent shifting movement o f said coupling element to maintain said teeth in engagement, said blocker in another position thereof allowing shifting of said element to di'sengage said teeth.

4. In power transmission mechanism, the combination of two relatively rotatable members and means for coupling said members together, said means comprising a coupling element between said members, teeth on said element and on one of said members to couple the element and member together, said element being spirally splined to the other of said members and being thereby adapted to be shifted in response to changes in relative direction of torque betweenl said members and impressed on said element through said teeth, and an oscillatable blocker having blocking portions effective. in one position of the blocker to prevent shifting movement of the coupling element to maintain said teeth in engagement, said blocker allowing shifting of the shiftable velement in another position of the blocker to disengage said teeth, a blocker control lever, and a spring biasing means for biasing the blocker in one or the other of its said positions depending on the position of said lever.

5. In power transmission mechanism, the combination of three relatively rotatable members and means for coupling either a first or second of said members to the third of said members, said means including a couplingelement effective between said third member and the others of said members, said coupling element being adapted to be shifted in response to changes in relative direction of torque between said third member and the others of said members to bring the coupling element into engagement with either of said :drst or second members, and an oscillat able blocker having blocking portions eective, depending on the position o the blocker, to prevent shifting movement of said coupling element in either of its positions in which it is coupled with said rst or second members,

6. In power transmission mechanism, the com bination of three relatively rotatable members and means for coupling either a first or second of said members to the third of said members, said means including a coupling element, teeth on said coupling element, teeth on each of said first and second members adapted to mesh with the teeth on said element depending on the position of the coupling element, said element being adapted tobe shifted in response to changes in relative direction of torque between either said lrst or second member `and said third member and transmitted through said teeth, and an oscillatable blocker having blocking portions efs fective, depending on the position of the blocker, to prevent shifting movement of said coupling element out of either of its positions in which its teeth are engaged with the teeth of either the first or second of said members.

7. In power transmission mechanism, the com# bination of three relatively rotatable members and means for coupling either a first or second of said members to the third of said members, said means including a coupling element.- teeth on said coupling element, teeth on each of said first and second members adapted to mesh with the teeth on the coupling element to thereby couple the element with either of said members,

helical splines on said coupling element and on .said third 'member and interengaging whereby the coupling element is adapted to be shifted in response to changes in relative direction of torque between vvsaid third member and the other members transmitted through said teeth, and an oscillatable blocker having blocking portions effective' to prevent shifting movement of said coupling element out of either of its positions in which its teeth are engaged with the teeth of said first or second members depending on the position of the blocker.

8. In power transmission mechanism, the combination of three relatively rotatable members and means for coupling either a first or second of said members to the third of said members, said means including a coupling element, said element comprising two portions movable toward and away from each other and a spring for yieldingly holding the portions apart, teeth on each of `said portions, teeth on each of said first and second members adapted to mesh with the teeth on one of said portions to thereby couplethe coupling element with either of said members, all of said teeth being beveled in the same direction and said spring holding said portions such a distance apart that the teeth on at least one of the portions are always in contact with the teeth on one of said iirst and second members, means coupling said coupling element with said third member and including helical splines on said portions and helical splines on said third member interengaged therewith whereby the coupling element is shifted in response to changes in relative direction of torque between said third member and the other members and transmitted through said teeth to engage one or the'other of said sets of teeth'on the element with corresponding teeth on said first or second members, and an oscillatable blocker having blocking portions effective on the splines of said coupling element portions tol prevent shifting movement of either of the latter portions out of its tooth engaged position depending on the oscillated position of said blocker, a shifting lever for oscillating the blocker, and spring biasing means for yieldingly holding the blocker in either of its oscillated positions. i

9. In power transmission mechanism, the combination of a driving element, a driven element. and means for completing two power trains of dierent speed ratios between said elements and including two different reaction members and gearing for driving said driven element at two diierent speeds in the same direction, a torque responsive brake for said two reaction members.

then coupled with the coupling element upon a reversal of torque.

10. In power transmission mechanism, the combination `ot a driving element, a driven element, and means for completing two power trains of dierent speed ratios between said elements and including two different reaction members and gearing for driving said driven element at two different speeds in the same direction, a torque responsive brake for said two reaction members, said brake comprising a stationary member, a shiftable coupling element eiective between said reaction. members and said stationary member, teeth on said coupling element, teeth on each of said reaction members adapted to be engaged by the teeth on the coupling element for coupling said coupling element and reaction members together, said coupling element being adapted to be shifted relative to said stationary member in response to changes in the relative direction of torque applied to' the coupling element through said teeth,- whereby to disengage the teeth on one reaction member and engage the teeth on the other reaction member, an oscillatable blocker having blocking portions effective to prevent shifting movement of said coupling element out of either of its positions in which its teeth are engaged with the teeth of either of said reaction members depending upon the position of said blocker, and means for effecting a change in the position of said blocker said brake comprising a stationary member, a

shiftable coupling element effective-between said reaction members and said stationary member and adapted to couple either of the reaction members with said stationary member depending upon the position of said coupling element, said coupling element being adapted to be shifted in response to changes in the relative direction of torque between theV reaction members and said stationary member, an oscillatable blocker having blocking portions effective to prevent shifting `movement of said coupling element in one direction or the other depending upon` the position of said blocker, and means for effecting a changein the position of said blocker to permit shifting of said coupling element bythe reaction of said gearing on the reaction member to permit shifting of said coupling element by the reaction of said bearing on the reaction member then coupled with the coupling element upon a reversal of torque.

l1. In power transmission mechanism, the combination or a driving element. a driven element, and means for completing two power trains of different speed ratios between said elements and including two different reaction members and gearing for driving said driven element at two different speeds in the samev direction, a torque responsive brake for said two reaction members, said brake comprising a `stationary member, a shiftable coupling element effective between said reaction members and said stationary member, teeth on said coupling element, teeth on each of said reaction members for interengaging with the teeth of the coupling element to couple the coupling element with either of said reaction members, interengaging helical splines on said coupling element and on said stationary member, whereby the coupling element is adapted to be shifted relative to said stationary member in response to changes in the relative direction of torque between either of the reaction members and the stationary member transmitted through said teeth, an oscillatable blocker having blocking portions effective on the splines of said coupling element to prevent shifting movement of said coupling element from either of its positions in which its teeth interengage with teeth of one of said reaction members, depending upon the position of the blocker, and means for effecting a change in the position of said blocker to permit shifting of said coupling element by the reaction of said gearing on the reaction member then coupled with the coupling element upon a reversal of torque.

12. In power transmission mechanism, the combination of a driving element, a driven element, and means for completing two power trains 11 dierent speeds in the same direction, a torque responsive brake for said two reaction members, said brake comprising a stationary member, a shiftable coupling element effective between said reaction members\and said stationary member, said coupling element comprising two portions movable toward and away from each other and a spring for holding the portions apart, teeth on each of said portions, teeth on each of said reaction members adapted to be engaged by the teeth on one of said coupling portions, helicalsplines bh each of said coupling portions and on said stationary member and being in interengagement, whereby said coupling element is adapted to be 'shifted in response to changes in relative direction of torque between the `reaction members and .the stationary member, said teeth on the coubling element and on the reaction member having ends beveled in the same direction and said spring maintaining the coupling element portions apart so that the teeth of the latter portions are always in contact with the teeth of at least one oi said reaction members, an oscillatable blocker having blocking portions effective on the splines of said coupling element portions to prevent shifting movement of either of the portions to disengage its teeth from those of the corresponding reaction member, depending on the position of the blocker, and means for effecting a change in the position of said blocker to permit shifting of said coupling element by the reaction of said gearing on the reaction member then coupled with the coupling element upon a reversal of torque.

13. In power transmission mechanism, the combination of av driving element, a driven element, and means for completing two power trains or different speed ratios between said elements and including two dierent reaction 'members and gearing for driving said driven element at two different speeds in the same direction, a torque responsive brake for said two diierent reaction members, said brake comprising a stationary member, a coupling element eective between said reaction members and said stationary member, said coupling elementA comprising two portions movablc toward and away from each other and a spring yieldingly holding said portions apart, teeth on each of said coupling portions, teeth on each of said reaction members adapted to be interengaged by the teeth of one of said coupling portions, the teeth on said coupling portions and on said reaction members being beveled on their ends in the same direction and said spring holding the coupling element portions apart such a distance that the teeth on the coupling element are Aalways in contact with the teeth on at least one of said reaction members. interengaged helical splines on said coupling portions and on said stationary member, whereby said coupling portions are shifted in response to changes in relative direction of torque impressed thereon through said teeth, an oscillatable blocker having blocking portions effective on the heli-` cal splines on said coupling portions to preven shifting movement of either of said coupling portions to bring the teeth of the portion out of interengagement with the teeth of the correspond-7 ing reaction member depending on the position of the blocker, means including a shifting lever i Afor oscillating said blocker to permit shifting of said coupling element by the reaction of said gearing on thereaction member then coupled with the coupling element upon a reversal of torque, and spring biasing means for holding the blocker in either of its blocking positions.

HOWARD C. WIEMER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,654,432 Rowledge Dec. 27, 1927 1,954,200 Fromm` Apr. 10, 1934 2,068,776 Syrony Jan. 26, 1937 2,127,305 Nabstedt Aug. 16, 1938 2,248,133 Snow July 8, 1941 2,371,564 Wemp Mar. 13, 1945 FOREIGN PATENTS Number Country Date 460,149 Great Britain Jan. 19, 1937 Certificate of Correction Patent No. 2,440,625. April 2, 1948. HOWARD C. WIEMER It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Column 6, line 34, for the Word shaft read shafts; column 10, line 33, claim 10, for bearing read gearing; column 12, line 4, claim 13, for of after teeth read on; and that the said Letters Patent should be read with these corrections therein that the seme may conform to the record of the ease in the Patent Oce.

Signed and sealed this 13th day of July, A. D. 1948.

THOMAS F. MURPHY,

Assistant Uommz'ssz'oner of Patents. 

